Gary Winters, 45, posted a series of heartfelt messages on the social networking site urging people to rally round to find the 51-year-old who, has now been missing for ten days.
Mr Winters, who is understood to have split up with the NHS worker just days before she vanished, said he had conducted a comprehensive search of woodland walks and begged God for her safe return.
Heather McKay was last seen in Dechmont, Broxburn, with the disappearance of the “bubbly, sociable” mum described as “entirely out of character”.
On the day she went missing, Mr Winters wrote: “Please help to find Heather, missing all day, if you see her please get in touch.”
The next day he posted: “As you all know, Heather has gone missing.
“We are into our second day now, any help would be great. Please message me or Heather’s family or friends if you see or know anything please x.”
Last Saturday he updated: “Sorry I can’t repost, my laptop is in for repair. Please keep reposting, we need all the help.” He later added: “Heather McKay a full search done of the cottage and woodland walks done by myself and the police please help xxx”
Last Sunday he wrote: “Now day three, please help. Missing and missed, please help Heather McKay. Message all friends and family xxx.”
His poignant last message – posted on Monday – simply said: “All I ask is Heather McKay is returned safe today and well, please God please xxx.”Ms McKay was on annual leave from her job at the NHS and was staying with a friend in Dechmont when she disappeared. She was last seen at 7.30am on Friday. When another friend called at the address an hour later Ms McKay was not there and had left her mobile phone behind.
In an emotional appeal on Friday, her children Andrea and Kevin Waddell pleaded with her to come home.
Andrea, 24, said her mother had been in a “short-term” relationship which had come to an end and had “perked up” after initially being “quite low”.
She added: “I don’t think [the break-up] is anything to do with what has happened. My dad passed away in 1999, so she just wouldn’t do this. She has been there for us ever since. She’d always talk to me. We’re more like sisters, best friends, than mum and daughter.”
Andrea and Kevin have put up posters in a bid to find their mother and have now set up a Facebook page which has been joined by 7600 people. The hashtag #findheather is trending on Twitter.
Police have issued several appeals for information relating to the disappearance but say there is “no suggestion of criminality or foul play”.
Ms McKay is described as around 5ft 7in tall, medium build with hazel/green eyes and brown hair.